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The TT60 is under 50K, but if I were you with that small load I would look into a small ci boiler, the amount of energy you will use to heat that space will never pay off with a mod con...

think of it this way...

A prius gets 55 mpg and costs $30K a comparable small no hybrid car gets 40 mpg and costs $15K, you only drive 8 miles a day, you would not be doing yourself any favors buying a hybrid, now if you drive 300 miles a day it would be a smart move...

Mod cons will not last as long as a ci, will cost more to maintain, ect...

look into the small Weil Mclain golds, cg series...

For example a WM CGI25 {net is around 37K BTU's}, piped primary secondary, with bumble bee pumps, an outdoor reset {either the hydrostat, a taco 700, or which ever you choose}, outside combustion air, ect you will only be losing the so called combustion efficiency difference which is around 10% {I would say more like 3-6% in the real world}, so if you are spending $600 a year to heat your space you will save a maximum of $60 a year, but now factor in the ci will last 40 vs 20 or so for a mod con, the ci will go years with out service vs the mod con will not.. And the ci will save you time, money on the install, money on maint., ect..ect..ect..

pay more attention to the minimum modulation rate than the nameplate (maximum) rating. Here's a short list of available options, though there may be others. Minimum firing rate is in [square brackets] and maximum in (parentheses.) My current working hypothesis is that the minimum modulation rate should be no more than one third of the design day heat loss (less is better.)

The lower initial cost of a cast iron non-condensing boiler is a compelling argument. It will also allow for smaller less expensive panel radiators.

Here's the Twist which may support one boiler style (condensing) over the other (non-condensing)....this 30,000 load is for a duplex and the two apartments need to be split into two zones with a 60/40 split of the load. On top of that, they are small apartments ( a two bed and a one bed). One of the bedrooms in the two bedroom apt. is 8x11. That's small and with a fair amount of solar gain, it should have its own zone.

This building will be well insulated and tight. Cooking in the kitchens can heat the apts. up.

How well suited is one style of boiler over the other when the possibilities of very small loads (one zone) will be the only call for heat?

I see homeowners that get sold into mod cons when there were much better options for much less money.

For example, a 5-6 year old-ish Knight mod con, installed in a 3 bedroom home {1200sq}, needed a board and a fan after 6 years, the parts were over $1500!!!! And then they told me when they compared heating bills vs their old leaking boiler they were only saving about $20 a month!!!!

Like I said if you had a much larger heat loss it can start to make sense, but IMO mod cons have a ways to go before they are the answer to every question...

A small ci boiler can be installed to run efficiently, people get hung up on the 95% vs 85% numbers, the fact is a lot of the mod cons I have seen need annual service, while a ci boiler can go 40 years without being cleaned {I have a 25 year old gas furnace that has never been touched in one of my rental properties and I have seen many boilers that go their entire life without being cleaned or serviced {besides maybe a circ or sr}...

Look into the CG boilers, if you want a little more comfort and efficiency, run them with an ODR, pipe them pri/sec with delta t circs... I have done many installs this way and the units shine, last June I installed 4 of them small 25's with 4 Rinnai tanklesses in a 4 unit building , the apartments were 750-900sq ft and they were all warm all winter with endless hot water. They didn't get odr or anything fancy and I'll bet no one complained about what it cost to heat their apartments...

I would make the zones as large as possible no matter what boiler you go with, a ci will be more "forgiving" to small loads than a mod con will.

Holds a lot of water. One has to look at system as a whole small zones verse single zoned systems. Micro zones can kill boiler efficiency.

heatpro the ability to modulate to the load means tons in savings verses the added condensing efficiency. It is also deeper than 85 verse 95 percent efficiency. A bang 100k btu fire no matter the load burns more than coming on line at 25k to match the load.

Peoples claims to saving, or the lack of has to be taken with a grain of salt. Most people just look at the bill with out realizing gas cost difference, or weather from year to year.

Ideally a nice design that flows very well, and needs very little field supplied piping...

I really want to see them switch to a more convenient control system too, I wish Honeywell would make a mod con control that works for all the units, plug it rite into an exp zone control and odr and just have the boilers control handle modulation, safety, and high/low/diff limits...

What scares me is parts support in 30 years, for example a tt excellence control, if the units are still holding water in 30 years and the control gives up will there be one on the shelf somewhere, when at the current rate they will be on their 6th or 7th control...

If it was as easy as plugging in a new Honeywell unit and maintaining some taco controls for zoning and odr the parts would be readily available, less expensive, and all techs would be familiar with them since they wouldn't vary much... The modulation could be handled with pill modules or a direct upload form an internet download from each manufacturer... I'm not an engineer but I am sure it can be done, all the sensors would be the same, all the controls, it would be a perfect world...

I just went thru my first winter with a Loch WH55 installed in a home with a heat loss of around 25,000-Being oversized by double, I can say there were no problems, no short cycling-Actualy, being oversized allowed the boiler to operate at only 30 to 50 percent, never any more, never maxing down to 20 percent for more than a couple of minutes in warmer weather, but climbing right back up to 30 percent for most of the cycle. For me, this is great, as the boiler is much quieter operating in these lower ranges. For anyone installing one of these in there living space, this is important, as they are not always whisper quiet, especially on start up, and shut down-

is the heat load so small ? If the answer to this question is because it is very tight and insulated well may determine or make one type boiler more acceptable . If the house is that tight it may be unwise to use a CI boiler . Mod cons and the style of venting they offer are a better fit for a very tight house . Is this house old or new and did it have a masonry chimney prior if it is old .

You didn't get what you didn't pay for and it will never be what you thought it would . Langans Plumbing & Heating LLC 732-751-1560 Serving most of New Jersey , Eastern Pa .Consultation , Design & Installation Rich McGrath 732-581-3833

I heat my home with Rinnai Energysaver Direct Vent wall furnaces. I have two units that will each modulate from 8200-20,500 btu and modulate on the fan as well. Simple install, highly reliable. Under 40kbtu, they are hard to beat. I understand that most here are "system" guys, but these should be another tool in the tool bag.

When I put that strong a pitch out I have to acknowledge my bias as I represented them for over 20 yrs and still consult with them, but I've also heated my homes, basement and garage with them for all of that time. Anyway, they are worth consideration.

Installers and homeowners tend to pay too much focus to the heating plant and the boiler room. They also don't develop what I call long term heating system upgrade plans.

There's a lot of throwing about percentage numbers about savings in retrofit systems and many lose site of opportunity. I never for the most part see us talking about water temperature. HeatPro always brings in the small cast iron boiler and many others about the low end of the modulation rate. As SWEI pointed out that is generally the culprit and cause of short cycling, not the high end. Boiler will never get out to the high end if the system doesn't ask for it.

The opportunity I'm talking about is this. How many of you have walked into a home with simple residential baseboard where the homeowner wants a Mod/Con and all you give them is the Mod/Con? The boiler is just a heating plant, it makes energy and that for the most part is its job period. There's an entire system out their that needs the same upgrade as you just did in the boiler room.

Sit back and think about your last 5 installs. Was there an opportunity in any of them to develop a long term heating system upgrade. At the time you quoted the job, did you give the customer options to changing out that residential baseboard for high capacity board to get that water temperature down? No, Why not? Maybe you thought they couldn't afford it or maybe you did offer and they couldn't. Why not give the consumer the number to change it out, tell them to put away their pennies for next year and change out Zone 1. Maybe the following year Zone 2 and so on. Provide the customer with continually upgrades that will show in their utility bills year after year. Maybe even throw in that yearly service for free at the time you do these upgrades giving the customer even more value.

There are plenty of opportunities and tools available to continually upgrade a heating system. It doesn't mean just the boiler and this is an opportunity that in my opinion is missed daily.

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

The house is old, 1945, and small and its a rowhouse so the only exposure is the front and back wall and the roof.It has a chimney flue for the existing...drum roll please...two 75k furnaces which are way oversized even before its upcoming insulation/new window work. Those furnaces would create tornadoes in the apartments with air blowing out from behind switch plates and outlet covers and gaps in the baseboard.

If I were to go into a home and tell them "I can rip out all your perfectly working baseboard for X amount and reinstall a board that will allow you to drop the boiler temps an average 20 degrees" they are going to have 2 questions {if they are interested} first how much does it cost and second is how much does it save..... You do the math and let me know how much someone can save with a 1400 sq ft home spending $1100 a year to heat it with a ci boiler.. Unless you install HO board for much less than me, I am thinking their kids will have to live well into their 70's to pay for it, lol....

I actually make it a practice to install an additional coil on existing hydro air mod con retros, and I over size new systems when the budget allows, the sad part is most of the time when I do new construction it is for the GC and I never speak to the HO, so mentioning lowering boiler temps to the GC is going to just waste mine and his time because at the end of the conversation he is going to ask if it works both ways and if I can put a little less board and run the boiler hotter, to save him money.....

Here is what I always mention a small ci for... With properties that have short heat losses, you don't spend much for heat, so the additional costs that I personally see in the field, is hard to justify for such a small savings... Don't get me wrong, I install a lot of mod cons, but I do my best to put myself in the customers shoes, if he has a 30K BTU load and wants to save money, I am going to show him other places that will save him more than a mod con, for example {fake numbers} say a mod con install is $10K and a ci is $5K, I will show him how we can install the ci boiler and spend the other $5K on tightening up the envelope, new doors, windows, insulation, aux heatpumps, aux coal stove, ect... Or I will show him how he can spend it on something to make him more comfortable, central A/C, a new massaging recliner what ever...

I do believe in making the entire system work well, I have a deposit on a job where the heatloss was $58K BTU's, they have oil/steam and I am installing gas hydro airs with heatpumps and a Rinnai tankless. I gave him the price both ways with a mod con and without, and he asked if he was better off with the mod con and no heatpumps or the heatpumps and the ci, because he couldn't afford both... I told him I would do the ci and the heatpump- a few reasons, aux heat is nice, when your boiler is down you can run the heatpump as a back up- Heatpumps are inexpensive to run in the shoulder seasons {even compared to a mod con}- Boiler runs less with heatpumps- CI will last longer than mod con- Ci will cost less to maintain- CI will be more reliable- CI will be easier to repair he gave me the deposit for the heatpump/CI system..

Like I said, I do MANY mod cons, more than most companies around here, BUT IMO they are not the answer to every hydronic question... I have a solo 175 in my house, and had a gb before I switched {it was still new but I started selling tt's}, but I heat with LP and my house is over 4K sq ft, so 10% fuel costs can be $700 a year, with a 1100sq ft home on nat gas, 10% a year can be $75 a year, takes a lot of year savings under $100 a year to make up for the cost diff, and if that unit cooks a $850 board at year 5, let me know how happy your customer is when he breaks out the calculator....

TO me a mod con starts making sense around 70K BTU's with LP and 100K BTUs with nat gas, and even then if a board goes or a $700 fan, or the unit needs annual service like some of them do, it starts to not make sense fast... Now if the customer is a techy, very interested in being green, has no room for a ci, wants fancy, money is no object, ect then sell them what ever they want to buy, but when I walk into a house, for the most part I see a confused customer just looking to save some money over the life of his mortgage, trying justify spending almost double the cost upfront to save some money 6 months a year, I take it personally, and I have showed customers that putting the extra money down on their new home will save them more than any mod con can over the 30 year term, you would be shocked to see what an extra 5K saves you in 30 years!!!

Now I know there are rebates available that help with the costs, but I have yet to priced one where it made up for the difference {more like 20% of it }, other places may be different...

$461,511.57 over 30 years, now put $5K down so enter 200K value with $195K loan amount total of 360 payments will be $451,848.78, you just doubled their money with no risk... Now I know a ci can break too, but in my experience mod cons have a ways to go before they are 30-40 year machines...

installers and designers have a way to go before they know how to make any boiler and the system it is used in last 30 - 40 years . I think the machines are up to the task now .

What would you suggest they do with the existing water heaters when they take 25-30 K worth of heat out of these chimneys ?

You didn't get what you didn't pay for and it will never be what you thought it would . Langans Plumbing & Heating LLC 732-751-1560 Serving most of New Jersey , Eastern Pa .Consultation , Design & Installation Rich McGrath 732-581-3833

Install a decent air remover {correctly}, check and treat the boiler water, do the math and run the proper minimum boiler pressure, make sure there are zero leaks, install as much ss, copper, and brass as possible {stay away from ferrous metals when possible, less rust is better}, install quality components and isolation valves at each component so when there is problem you can do it without draining the entire system {this keeps you from adding new water to the system}, install the correct venting correctly, install the unit high if there are water issues, and use a separate DHW machine...

For DHW I would use a Rinnai tankless... the heating unit will only run the heating season, no reason to run a heating boiler year round for DHW, having the unit shut off for 6 months every year will help it last longer...

So if you pay a little attention to these details you can easily get a decent ci boiler to go the 40 plus mark, I have some g115's out there that I installed and am confident they will still be in them basements in 45 years, we service them annually and see their condition some are already almost half way there and look brand new in and out!!!! I know this because I pulled one out of a house last year after the house flooded, the boiler was installed 10-15 years ago with untreated well water and when I put the borescope inside it looked BRAND NEW!!!

So protect the boiler with primary secondary piping, test and treat the water {fernox has a lot of options}, introduce as little new water once the system is in commision as possible, get all the air out, run the minimum temps and pressures, keep the steel and cast to a minimum, make sure its combustion is perfect, ect and these systems will last a long time...

What scares me about the mod cons we are seeing is the cost of components, the rate the components change, and the thin-ish heat exchangers.

Double the thickness of the HX's (thats not going to double the price of the unit}, get taco or honeywell ect to make an all in one mod con control so we know it will be available in 30 years and not cost more than a new boiler, keep it all very simple, supply sensor, return sensor, gas valve, done. {with of course the safety switches in there too}.

But the key would be basic gas valve, ignition, control, and venting components that interchange with other brands... We could keep a box of parts on the truck for all mod cons like we do with ci boilers, the boiler manufacturers can go back to designing hx's and insulated jackets...

I know there are some guys on here and contractors out there that just want to install mod cons all day, I can't blame you, they are light, clean, easy to install, and the profits reflect the opposite, BUT do the math, if the house is getting A/C or has an existing a/c system, install a heatpump for the shoulder seasons and a ci boiler for the heating season with a separate unit for DHW.

Sure the ci will not modulate BUT it doesnt have to, your ci boiler is only going to be running in the colder months, in the shoulder months where the unit would be modding to the basement you heatpumps are working. This type of system saves money and will get your customer 40+ years out of their ci boiler... Sure that isn't the best for your business plan since you will most likely not live long enough to change the boiler again, but that is fine with me as long as it is good for the customer...

With a CI install, is there any benefit to adding a storage tank somewhere in either the primary or secondary loop or at the junction of the two for the purpose of reducing cycling and extending boiler run time?

A small buffer (storage) tank is a great idea . It essentially gives you hydraulic separation between the boiler and the system . You can make that the device that calls for heat so that the boiler never short cycles either . 180*+ water boiler shuts off , when the tank says 155* boiler turns on . You have mass , the boiler will run nice efficient cycles , no pain in the ass CSTs , you could put an I Series w/ ODR on the system side and lengthen the time between calls for heat to the boiler . Right off the top of my head I can say Caleffi and HTP both offer small 25 gallon storage tanks , and boiler buddy makes a really nice 30 gallon . A Delta T circ like a bumble bee would be real good for the boiler pump (little if any head loss) and of course whatever circs on the system side depending on conditions there . Don't forget quality air elimination , some buffers will perform this task very well , the 3 I mentioned certainly do

Post edited by Rich on May 2014

You didn't get what you didn't pay for and it will never be what you thought it would . Langans Plumbing & Heating LLC 732-751-1560 Serving most of New Jersey , Eastern Pa .Consultation , Design & Installation Rich McGrath 732-581-3833

and I recommend it for jobs on which there is an existing boiler in good shape, especially if the boiler is oversized (which roughly 95% of them are in my experience.)

BUT

I still maintain that the conventional boiler, ODR-controlled mixing valve, and the buffer tank together will cost at least as much as a basic mod/con boiler will. Not as much as a fully-featured mod/con perhaps, but even for that, we're down to a few hundred dollars here unless the venting gets overly complex.

For me to install a basic conventional gas boiler with a simple close spaced tee p/s system, add an os100 ODR sensor to the hydrostat, ect it is around half of what I would get for a TT solo60 installed... By the time I build the wall paint and mount the board hang everything, I could have the ci boiler almost done... Plus the boilers are twice the cost....

On another note, I dont like adding buffer tanks to small resi systems, as most of you know from my posts, I am not a fan of tanks in general, they just don't last anymore... The added expense of the tank its piping and control to me doesn't make sense. Now of course I end up installing them where they are needed, but I will first try to figure a way around the short cycling, there are a few options for getting longer run times out of systems that don't involve storage tanks...

I installed a gb162 in a large house a few years back, they had 11 zones and 3 or 4 of them were very small, bathrooms and hallways with their own t-stat... So I mentioned to them that it could be a problem and I was working off another contractors proposal so I was told we could deal with it if it arose...

sure enough that thing constantly cycled, clicking in and out not liking them short bb runs that probably called more than any other zone in the house...

So with some fancy control work, a few thermostat changes, I got the system to work without adding a tank, I want to say that boiler was installed 6 years and all is still well, now I have seen others that I went to or service calls, with a lot of faulty parts, I have to think from the boilers constantly cycling on and off, if you want your mod con to last, figure out a way to get the longest run times possible, but if adding a buffer tank is the only option, add in the cost of changing that tank once and a while.. A friend of mine just changed a 4 year old boiler buddy, I thought it would be under warranty but it turns out 3 years on the BB tanks!!! Buying a $1000 tank every 5 years would make me sick..

It seems the older tanks {like most things} last longer than the stuff made now, but I can not count the ss indirects, buffers, electric/gas/oil fired tanks that I have replaced under warranty, and the amount of tanks I replace a year or 2 after warranty are even higher. My aunt bought a house with a gas water heater installed about 15 years ago when she bought the house the tank was 6 years old and its still there, so there are some that will last but for the most part I am not happy with what i see from water tanks...

But yes it seems some last, just its luck like anything else, My sister has a lincoln LS with 190K miles on it, 90% of the others built needed engines before 80K....

Can any of those tank in tank water heaters be used for both hydraulic separation and load buffering? The primary fluid storage is often quite a bit. The brochure for TT's multi energy series, for example, seems to illustrate several examples where the tank is acting as the hub for the system. But that tank comes with an extra coil for solar, etc, it's not a basic model.

As much as I love them for DHW, I have not been able to find a really good way to use them in a combined buffer/indirect application. The SME versions are quite pricey and for my money are not sized right. For solar and biomass applications, I'd rather see something the size of the SME 120 but with 119 gallons of primary (solar) and 52 of DHW.

which is the better position, in the primary or the secondary or where the two meet?

I'm thinking that if its in the primary with a CI boiler and the primary circulator is running because there is a call for heat, then there could be heat lost as the water passes through the boiler while its not firing and waiting for the water to cool down.

the only call for heat recognized by the boiler should be a call from the storage tank . The boiler circ should never run except during a call . The other circs will not push / pull water from the boiler , this is the de coupler of the circuits . Systems tend to get too involved when too many have an opinion . We all can probably agree that oversizing is bad . But what if someone made a piece of equipment that was a buffer tank , boiler , plumbed easily , and was affordable and space saving would there be a great debate ? Have a look at the following link , really think about what this would offer . I use these many times and have had trouble free operation , customers love their gas bills and they are affordable . Let me know what you think Stenty

You didn't get what you didn't pay for and it will never be what you thought it would . Langans Plumbing & Heating LLC 732-751-1560 Serving most of New Jersey , Eastern Pa .Consultation , Design & Installation Rich McGrath 732-581-3833

Just to give you an idea of how much a modcon install will run, I spent $7,000+ on materials, including a 20 gallon Superstor, for near boiler work. The Lochinvar was maybe a third of those cost. However, I am saving at least 40 percent on fuel, going from an old, oversized, steel, oil fired boiler, to a propane fired modcon.

Given the input rating max of 50kbtu the hot water is limited. That said, it will make 2.1 gpm at a 75* rise all day long. At use temperature that will make approx 2.5-2.7 gpm. The owner/tenant decides whether it is sufficient and how it is used. That is the issue with combis. Frequently, the first question is how much hot water do I need? You compare high hot water output to how upside down that makes you on the heat side by the time you have a large enough combi to deliver "enough hot water".